Virtual Inheritance in C++

#include <iostream.h>

#include <conio.h>

class base

{

      public:

      virtual void vfunc()

      {

            cout << "This is base's vfunc().\n";

      }

};

class derived1 : public base

{

      public:

      void vfunc()

      {

            cout << "This is derived1's vfunc().\n";

      }

};

/* derived2 inherits virtual function vfunc()

from derived1. */

class derived2 : public derived1

{

      public:

// vfunc() is still virtual

            void vfunc()

            {

                  cout << "This is derived2's vfunc().\n";

            }

};

int main()

{

      clrscr();

      base *p, b;

      derived1 d1;

      derived2 d2;

      // point to base

      p = &b;

      p->vfunc(); // access base's vfunc()

      // point to derived1

      p = &d1;

      p->vfunc(); // access derived1's vfunc()

      // point to derived2

      p = &d2;

      p->vfunc(); // access derived2's vfunc()

      getch();

      return 0;

}

Virtual Functions # 2

#include <iostream.h>

#include <conio.h>

class base

{

      public:

      virtual void vfunc()

      {

            cout << "This is base's vfunc().\n";

      }

};

class derived1 : public base

{

public:

void vfunc()

      {

            cout << "This is derived1's vfunc().\n";

      }

};

class derived2 : public base

{

      public:

      // vfunc() not overridden by derived2, base's is used

};

int main()

{

      clrscr();

      base *p, b;

      derived1 d1;

      derived2 d2;

      // point to base

      p = &b;

      p->vfunc(); // access base's vfunc()

      // point to derived1

      p = &d1;

      p->vfunc(); // access derived1's vfunc()

      // point to derived2

      p = &d2;

      p->vfunc(); // use base's vfunc()

      getch();

      return 0;

}

Pure Virtual Function

//A program to illustrate how to declare a pure virtual function and equate it to zero as it

//   does not have any function parts.//

#include <iostream.h>

#include <conio.h>

class base {

   private :

      int x;

      float y;

   public :

      virtual inline void getdata() = 0;

      virtual inline void display() = 0;

};

class derivedB : public base {

   private :

      long int rollno;

      char name[20];

   public :

      void getdata();

      void display();

};

void derivedB :: getdata()

{

   cout << " enter roll no of student \n";

   cin >> rollno;

   cout << " enter name of a student \n";

   cin >> name;

}

void derivedB :: display()

{

   cout << " roll number, stdent's name \n";

   cout <<  rollno << '\t' << name << endl;

}

void main()

{

  clrscr();

   base *ptr;

   derivedB obj;

   ptr=&obj;

   ptr->getdata();

   ptr->display();

   getch();

}